Adverse drug events (ADEs) associated with over-the-counter (OTC) medications cause 178,000 hospitalizations each year, representing a major patient safety concern. Older adults, aged 65+, one of AHRQ's priority populations, are particularly vulnerable to ADEs. Of the 2.2 million older adults considered at risk of a major ADE, more than 50% were because of concurrent use of an OTC and prescription medication. However, no effective interventions have attempted to decrease harm associated with OTC medication use in this population. We propose to implement and evaluate a system redesign intervention to decrease high-risk OTC medication misuse. This intervention will reduce misuse by improving communication between older adults and community pharmacists via the following features: a redesign of the store's physical environment to sensitize older adults to high-risk OTC medications, and the implementation of a clinical decision tool to support the pharmacist when critically evaluating the older adult's health status. Our hypothesis is that older adults who are more aware of risks and can more easily determine if that risk pertains to their own health situation by speaking with a community pharmacist will be more knowledgeable in their OTC selection, which will in turn lead to safer OTC use. Our specific aims are: 1) to refine the system redesign intervention and implementation strategy through diagnostic and formative evaluation, 2) to evaluate the effectiveness of a refined system redesign intervention on preventing misuse of high-risk OTC medications by older adults, and 3) to evaluate the implementation of a refined system redesign intervention in community pharmacies. The study will be conducted in three mass-merchandise stores with onsite pharmacies. We will refine the intervention (Aim 1) by eliciting feedback from older adult and pharmacy stakeholders, and by implementing the system redesign on a small scale in one store. Next, we will use a pre/post design to test the system redesign intervention and evaluate its implementation in two pharmacies (Aims 2 and 3). Observations, surveys, and interviews will be used to assess the intervention effectiveness and the implementation strategy. This study is significant and innovative for several reasons: our highly experienced and multidisciplinary team includes members from pharmacy, nursing, public health, engineering, and medicine; we will use human factors engineering theories and methods to design and implement a patient-centered intervention; and we are partnering with a community pharmacy committed to improving health, wellness, and self-care in its communities.